Understanding Circuit Analysis Equations: Step-by-Step Guide

[brittydagal]

Homework Statement

Alrighty, my question is the exact same one that is written in this post - https://www.physicsforums.com/showthread.php?t=528337

The issue I'm having is understanding how to make/write my equations. I guess I just don't understand how you can know which way the current goes when you hit an intersection. I would LOVE it if someone could go through how they decided what the equations equal. I understand that you start at the battery (or at least I like to) and I usually move from - to + on the battery and then try to track the current but I get confused! I would show you my photo of the current but I changed it a million times so it looks pretty weird.

Anyways- Can anyone give me the super detailed, step by step?

Thanks- Studying for exams :P

Homework Equations

P = IV
V = IR

 

[CWatters]

I just don't understand how you can know which way the current goes when you hit an intersection

As long as you are consistent with your notation it shouldn't matter which way you assume the current will go. If you define one way as +ve and your assumption turns out to be wrong the value you calculate will be -ve.

Try defining the currents so that you can write I1 + I2 + I3 = 0 rather than trying to guess the direction and writing I1 + I2 = I3